[amsat-bb] The laws of physics.

John Hackett archie.hackett at hotmail.com
Thu Oct 11 00:34:54 PDT 2007

Due to it's somewhat erratic behaviour this past week I have been monitoring AO-7 even more closely than usual.

There has been some controversy as to which mode ... B, C or OFF  ... AO-7 is in at certain periods in the same orbit.

Here are a few points to ponder.

This is a good opportunity to test your receiving system.

Some stations report the satellite as being OFF when they can't hear their own downlink ... whereas others, at the same time/same orbit report it as being ON but in mode-C ... (low power) ... this is *NOT* a comment on SV1BSX's report of the satellite being OFF ... because I experienced exactly the same thing myself this morning at 11-10-07 at AOS.

AOS ... nothing heard ... (and I gave *GOOD* antennas) ... but soon after the "footprint" crossed the grey line, in both IT and NOVA ... (I was monitoring both) ... my own downlink was audible AND INCREASED PROGRESSIVELY AS THE SATELLITE APPROACHED THE HORIZON (LOS)... that is to say ... the range increased and the signal became stronger.

For obvious reasons, THIS DOES *NOT* SUGGEST MODE-C.

The laws of physics *DON'T* change ... however, propagation and other parameters do. Mode-C. 

It is possible that the 30+ year old solar panels are producing enough power to run the transponder at 2 watts since they've been producing adequate power to run the transponder in mode-B ... whatever that power is these days ... (unknown) ... but it's still hyperthetical as to which mode the satellite is actually in at AOS.

If anyone has any coherent explanations please share them with us because once again AO-7 is continuing to dish out surprises and the old girl can teach us all something valuable for future satellites.


It's interesting to note that when the *footprint* crosses the grey line ... (a phenomenon I've monitored for several days now) ... the solar panels are in full illumination ... (theoretically !!!) ... but the transponder appears to be OFF and switches ON just as the footprint crosses the line.

A coincidence? ... I think not, but I don't have a "sensible" explanation.

Explanations are invited to EU-Amsat.

73 John.   <la2qaa at amsat.org>

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